Noxious Weeds in Manitou Springs

Common Tansy

Yellow flowers are numerous in flat-topped dense clusters at the tops of the plants. Button-like flower heads lack ray flowers. Flowering typically occurs from July to September. The leaves are alternate, deeply divided into numerous narrow, individual leaflets. Mature plants are 1.5 to 6 feet tall. Habitats for Common tansy include:

• Irrigation Ditch Banks
• Ornamental Beds
• Pastures
• Roadsides
• Streams
• Waste Places

Common tansy is designated as a “List B” species in the Colorado Noxious Weed Act. It is required to be either eradicated, contained, or suppressed depending on the local infestations. Learn more about Common Tansy (PDF).

Cypress Spurge

Leaves are linear, approximately half to 1.25 inches long and 1 to 2 millimeters wide. Upper stem leaves that occur near the inflorescence are yellow or yellowish-green in color. Leaves are stalkless, alternate, narrow and linear to lance-shaped. Stems are 4 to 32 inches high, hairless, green to yellowish green in color and branch in the upper portions. The leaves and stems emit a milky, toxic sap when broken. 

Humans should be careful and avoid contacting the plant with bare skin as it can cause skin irritation for some people. Cypress spurge is designated as a “List A” species in the Colorado Noxious Weed Act. It is required to be eradicated wherever found in the State. Learn more about Cypress Spurge (PDF).

Dalmatian Toadflax

A single plant produces 500,000 seeds, most of which fall within 18 inches of the parent plant. Seeds can remain viable for at least 10 years. Dalmatian toadflax grows to 3 feet, and has bright yellow snapdragon-like flowers with an orange throat on elongated racemes. The alternate leaves are broad, with a thick, waxy cuticle and a bluish cast. Each leaf is heart-shaped and wraps the stem. 

Habitats for Dalmatian toadflax include:

• Cropland
• Disturbed Open Sites
• Fields
• Forest Clearings
• Pastures
• Rangeland
• Roadsides

Dalmatian toadflax is designated as a “List B” species in the Colorado Noxious Weed Act. It is required to be either eradicated, contained, or suppressed depending on the local infestations. Learn more about Dalmation Toadflax (PDF).

Dame's Rocket

The flowers are white to purple with four petals and are clustered in loose terminal stalks. Flowers appear from May to August and the plant can produce seeds and flowers on any flower cluster at the same time. Leaves are slightly hairy, alternate, and 2 to 4 inches long. The leaves are lance-shaped with toothed margins. 

Habitats for Dame’s rocket include areas that have moist well-drained soils and full sun to light shade: 

• Disturbed Sites
• Ditches
• Gardens
• Open Woods
• Partly Shaded Woodlands
• Pastures
• Rangelands
• Roadsides
• Thickets

Dame’s rocket is designated as a “List B” species in the Colorado Noxious Weed Act. It is required to be either eradicated, contained, or suppressed depending on the local infestations. Learn more about Dame's Rocket (PDF).

Houndstongue

Flowers are reddish-purple (occasionally white) and droop slightly from densely clustered panicles. The five rounded petals are cupped by five sepals covered with long, soft white hairs. Flowering occurs May to July. The simple leaves are lance or oblong shaped, with a smooth edge and no teeth or lobes. Leaves are alternate, 1 to 12 inches long and 1 to 3 inches wide.

The leaf tip is sharply pointed, like a hound’s tongue, yet are covered with long-soft white hairs. Houndstongue is poisonous. Toxic pyrrolizidine alkaloids in Houndstongue stop liver cells from reproducing. Though the plant has a distinctive odor that repels animals, it is more palatable when dried. Houndstongue is designated as a “List B” species in the Colorado Noxious Weed Act. 

It is required to be either eradicated, contained, or suppressed depending on the local infestations. Learn more about Houndstongue (PDF).

Knotweeds

Are bright green, bamboo-like, perennial plants that grow 5 to 16 feet tall and spread through lateral root systems (rhizomes). Stems are hollow between nodes, and often reddish-brown and swollen at the nodes. Japanese knotweed leaves are broadly ovate or spade-shaped with low, bump-like scabers on the underside instead of hairs. Giant knotweed leaves are heart-shaped with long hairs underneath, and Bohemian plants typically have both leaf forms. The small, showy, greenish-white flowers develop on branched clusters and are present in late summer. 

Like other species in the genus Polygonum, the soil seed reserve is likely long-lived, and site monitoring should be carried out for at least ten years after the last flowering adult plants have been eliminated. All three knotweeds are designated as “List A” species in the Colorado Noxious Weed Act. They are required to be eradicated wherever found in the state. Learn more about knotweeds (PDF).

Myrtle Spurge

The leaves are fleshy, blue-green and alternate. Flowers are inconspicuous with yellow-green, petal-like bracts that appear from March to May. Myrtle spurge contains a toxic, milky sap which can cause severe skin irritations, including blistering. This plant is poisonous if ingested; causing nausea, vomiting and diarrhea. Wearing gloves, long sleeves, shoes, and eye protection is highly recommended when in contact with myrtle spurge, as all plant parts are considered poisonous. 

Myrtle spurge is designated as a “List A” species in the Colorado Noxious Weed Act. It is designated for statewide eradication. Learn more about Myrtle Spurge (PDF).

Oxeye Daisy

It is an erect, rhizomatous, creeping perennial that grows 10 inches to 2 feet tall. The basal and lower leaves are lance shaped and toothed with long petioles (leaf stem) and the upper leaves are narrower and clasp the stem. The leaf size progressively decreases up the stem. Flower heads are mostly solitary at the end of the flower stalk and the flower head has 15 to 30 white ray flowers. Habitats for Oxeye daisy included:

• Meadows
• Native Grasslands
• Pastures
• Railway Embankments
• Roadsides
• Waste Grounds

Oxeye daisy typically grows in high elevations in Colorado. The site must be monitored for at least 10 years after the last flowering adult plants have been eliminated and treatments repeated when necessary. Oxeye daisy is designated as a “List B” species in the Colorado Noxious Weed Act. It is required to be either eradicated, contained, or suppressed depending on the local infestations. Learn more about Oxeye Daisy (PDF).